posix/unistd/exec.cpp

/*
 * Copyright 2008, Ingo Weinhold, ingo_weinhold@gmx.de.
 * Copyright 2004-2005, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
 * Distributed under the terms of the MIT License.
 */


#include <libroot_private.h>
#include <syscalls.h>

#include <alloca.h>
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


static int
count_arguments(va_list list, const char *arg, char ***_env)
{
	int count = 0;

	while (arg != NULL) {
		count++;
		arg = va_arg(list, const char *);
	}

	if (_env)
		*_env = va_arg(list, char **);

	return count;
}


static void
copy_arguments(va_list list, const char **args, const char *arg)
{
	int count = 0;

	while (arg != NULL) {
		args[count++] = arg;
		arg = va_arg(list, const char *);
	}

	args[count] = NULL;
		// terminate list
}


static int
do_exec(const char *path, char * const args[], char * const environment[],
	bool useDefaultInterpreter)
{
	int32 argCount = 0, envCount = 0;
	char invoker[B_FILE_NAME_LENGTH];
	char **newArgs = NULL;

	if (path == NULL) {
		errno = B_BAD_VALUE;
		return -1;
	}

	// count argument/environment list entries here, we don't want
	// to do this in the kernel
	while (args[argCount] != NULL)
		argCount++;
	while (environment[envCount] != NULL)
		envCount++;

	if (argCount == 0) {
		// we need some more info on what to do...
		errno = B_BAD_VALUE;
		return -1;
	}

	// test validity of executable + support for scripts
	status_t status = __test_executable(path, invoker);
	if (status < B_OK) {
		if (status == B_NOT_AN_EXECUTABLE && useDefaultInterpreter) {
			strcpy(invoker, "/bin/sh");
			status = B_OK;
		} else {
			errno = status;
			return -1;
		}
	}

	if (invoker[0] != '\0') {
		status = __parse_invoke_line(invoker, &newArgs, &args, &argCount, path);
		if (status < B_OK) {
			errno = status;
			return -1;
		}

		path = newArgs[0];
	}

	char** flatArgs = NULL;
	size_t flatArgsSize;
	status = __flatten_process_args(newArgs ? newArgs : args, argCount,
		environment, envCount, &flatArgs, &flatArgsSize);

	if (status == B_OK) {
		errno = _kern_exec(path, flatArgs, flatArgsSize, argCount, envCount);
			// if this call returns, something definitely went wrong

		free(flatArgs);
	} else
		errno = status;

	free(newArgs);
	return -1;
}


//	#pragma mark -


int
execve(const char *path, char* const args[], char* const environment[])
{
	return do_exec(path, args, environment, false);
}


int
execv(const char *path, char * const *argv)
{
	return do_exec(path, argv, environ, false);
}


int
execvp(const char *file, char* const* argv)
{
	// let do_exec() handle cases where file is a path (or invalid)
	if (file == NULL || strchr(file, '/') != NULL)
		return do_exec(file, argv, environ, true);

	// file is just a leaf name, so we have to look it up in the path

	// get the PATH
	const char* paths = getenv("PATH");
	if (paths == NULL) {
		errno = B_ENTRY_NOT_FOUND;
		return -1;
	}

	int fileNameLen = strlen(file);

	// iterate through the paths
	const char* pathEnd = paths - 1;
	while (pathEnd != NULL) {
		paths = pathEnd + 1;
		pathEnd = strchr(paths, ':');
		int pathLen = (pathEnd ? pathEnd - paths : strlen(paths));

		// We skip empty paths and those that would become too long.
		// The latter is not really correct, but practically irrelevant.
		if (pathLen == 0
			|| pathLen + 1 + fileNameLen >= B_PATH_NAME_LENGTH) {
			continue;
		}

		// concatinate the program path
		char path[B_PATH_NAME_LENGTH];
		memcpy(path, paths, pathLen);
		path[pathLen] = '\0';

		if (path[pathLen - 1] != '/')
			strcat(path, "/");
		strcat(path, file);

		// check whether it is a file
		struct stat st;
		if (stat(path, &st) != 0 || !S_ISREG(st.st_mode))
			continue;

		// if executable, execute it
		if (access(path, X_OK) == 0)
			return do_exec(path, argv, environ, true);
	}

	errno = B_ENTRY_NOT_FOUND;
	return -1;
}


int
execl(const char *path, const char *arg, ...)
{
	const char **args;
	va_list list;
	int count;

	// count arguments

	va_start(list, arg);
	count = count_arguments(list, arg, NULL);
	va_end(list);

	// copy arguments

	args = (const char**)alloca((count + 1) * sizeof(char *));
	va_start(list, arg);
	copy_arguments(list, args, arg);
	va_end(list);

	return do_exec(path, (char * const *)args, environ, false);
}


int
execlp(const char *file, const char *arg, ...)
{
	const char **args;
	va_list list;
	int count;

	// count arguments

	va_start(list, arg);
	count = count_arguments(list, arg, NULL);
	va_end(list);

	// copy arguments

	args = (const char**)alloca((count + 1) * sizeof(char *));
	va_start(list, arg);
	copy_arguments(list, args, arg);
	va_end(list);

	return execvp(file, (char * const *)args);
}


int
execle(const char *path, const char *arg, ... /*, char **env */)
{
	const char **args;
	char **env;
	va_list list;
	int count;

	// count arguments

	va_start(list, arg);
	count = count_arguments(list, arg, &env);
	va_end(list);

	// copy arguments

	args = (const char**)alloca((count + 1) * sizeof(char *));
	va_start(list, arg);
	copy_arguments(list, args, arg);
	va_end(list);

	return do_exec(path, (char * const *)args, env, false);
}


int
exect(const char *path, char * const *argv)
{
	// ToDo: is this any different?
	return execv(path, argv);
}